The subject matter disclosed herein generally relates to rotors for aircraft use. More specifically, the subject disclosure relates to balancing of main rotor blades of rotor craft.
For the rotor blade to operate properly in the dynamic environment in which it is used, the blade must meet requirements for balance so as to not result in excessive vibration levels when used in the rotorcraft. A typical rotor blade for a rotor craft, such as a helicopter or dual coaxial rotor rotorcraft is formed from several components including a spar with counterweights, a trailing edge pocket assembly including one or more skins, such as upper and lower skins, with a core therebetween, and a leading edge assembly including a leading edge sheath and other components. These components are typically secured to each other by a structural film adhesive bond and/or other fastener resulting in a blade assembly. Manufacture of the various components, and their assembly, introduces some variation in weight and weight distribution into the blade assembly. This variation is observed by measuring the weight and moments of the completed blade assembly via a balance procedure, often including a whirl fixture, in which the blade assembly is spun with a master rotor blade, having a selected weight and weight distribution. The rotation of the blade assembly is observed and compared to the master rotor blade, and any variation between the two is indicative of variation in weight or weight distribution of the blade assembly compared to the master rotor blade. Such variation is corrected in the blade assembly by removing material or counterweights, up to certain acceptable or feasible limits. The limits constrain how severe of an out of balance condition of the blade assembly can be corrected, resulting in potential of scrapping costly rotor blade assemblies.